Lost, gained, and regained functional and phylogenetic diversity of European mammals since 8000 years ago

Mammals have experienced high levels of human-mediated extirpations but have also been widely introduced to new locations, and some have recovered from historic persecution. Both of these processes-losses and gains-have resulted in concern about functional losses and changes in ecological communities as new ecological states develop. The question of whether species turnover inevitably leads to declines in functional and phylogenetic diversity depends, however, on the traits and phylogenetic distinctiveness of the species that are lost, gained, or regained. Comparing similar to 8000years ago with the last century, we show that extirpations and range retractions have indeed reduced the functional and phylogenetic diversity of mammals in most European regions (countries and island groups), but species recoveries and the introduction of non-native species have increased functional and phylogenetic diversity by equivalent or greater amounts in many regions. Overall, across Europe, the median species richness showed no change; median phylogenetic diversity increased by 0.7% over the last 8000years, while median functional diversity decreased by 0.6%. The balance of losses (extirpations) and gains (introductions, range expansions) has, however, led to net increases in functional diversity on many islands, where the original diversity was low, and across most of western Europe. Historically extirpated mega- and mesofaunal species have recolonized or been reintroduced to many European regions, contributing to recent functional and phylogenetic diversity recovery. If conservation rewilding projects continue to reintroduce regionally extirpated species and domestic descendants of extinct species to provide replacement grazing, browsing, and predation, there is potential to generate net functional and phylogenetic diversity gains (relative to 8000years ago) in most European regions.

Automated summary

Mammals in Europe have experienced significant changes in diversity over the past 8000 years, with extirpations and range retractions leading to reductions in functional and phylogenetic diversity in most regions, while species recoveries and introductions have increased diversity in many areas. Overall, there has been no change in median species richness, a slight increase in median phylogenetic diversity, and a slight decrease in median functional diversity. The balance between losses and gains has led to net increases in functional diversity on many islands and parts of western Europe.